Typhoon Mitag is expected to make landfall on South Korea's southwest coast on Thursday but its strength may be weaker than anticipated after passing through Taiwan and the Chinese mainland, the local meteorological agency said.

Mitag, the season's 18th typhoon and the seventh to affect the Korean Peninsula this year, could bring powerful winds and heavy rain to the southern parts of the peninsula, the Korea Meteorological Administration said on Monday, calling for thorough preparations to prevent damage.

Mitag was moving west-northwest from waters 410 kilometers south-southeast of Taipei at a speed of 16 km per hour as of 9 a.m. Monday. Its central pressure was reported to be 975 hectopascals, with a maximum wind speed of 32 meters per second. By 9 p.m., Mitag is expected to reach waters about 190 km south-southeast of Taipei while developing into a mid-strength typhoon.

KMA forecasters said Mitag is likely to reach the vicinity of Mokpo, South Jeolla Province, at around 9 a.m. Thursday after passing over land located about 340 km south of Shanghai at 9 p.m. Tuesday.

By the time Mitag makes landfall in South Korea, the typhoon is expected to have weakened to a small-scale storm, they said. Mitag will reach waters about 90 km east-southeast of Dokdo in the East Sea at 9 a.m. Friday, they added.

"The authorities are closely watching the movement of Typhoon Mitag as it could lose its strength and speed while passing through the coastal regions of Taiwan or China," a KMA forecaster said.

Meanwhile, weather forecasters on Jeju Island said the southern resort island will come under the influence of Typhoon Mitag beginning Tuesday. Rain of 30-50 millimeters per hour will begin on Jeju Island early Tuesday morning and a mix of strong winds and heavy rain is forecast for Wednesday. (Yonhap)